This invention relates to a circular stack sheet feeder with a lower loading tray, on which stacks of sheets arranged sheet-by-sheet can be loaded, comprising a conveying and reversing device, which transports the stacks arranged sheet-by-sheet in a first conveying direction to the lower side of a reversing cylinder and, with the help of the reversing cylinder, around this cylinder towards the top and, in a second conveying direction, onto a discharge tray over which at least one flexibly stretched conveyer belt is led, running in the second conveying direction, which passes between two rollers, arranged paraxially to the reversing cylinder, and with separating means which always pull the upper sheet of the stack vertically to the conveying direction of the conveyer belt.
Prior art circular stack sheet feeders of this kind actually have the advantage, in comparison with those where the separating means always move the upper sheet across the entire loading tray, that the loading tray is not only accessible from the two sides running in the conveying direction but also from the side running laterally thereto. However, this known circular stack feeder has the disadvantage that the upper sheet of the stack on the discharge tray will be maintained in a horizontal plane only for one predetermined sheet format or size and sheet-by-sheet arrangement. In this regard it should be understood that a horizontal disposition of the upper sheet is necessary for a safe functioning of the sheet separating device, as well as to accommodate the conveyer line which extends in the conveying direction. Consequently, the prior art sheet feeders of this type cannot be utilized under conditions where it is necessary to feed sheets of varying format and arrangement, such as in connection with a folding machine, because such sheets which differ in size or arrangement from the predetermined criteria will assume an inclined disposition in the discharge tray rather than the necessary horizontal disposition.